1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method. More specifically, the present invention relates to a method for tracking an object by using an image.
2. Description of the Related Art
A conventional method for tracking an arbitrary object uses a pattern matching method, which searches for an area having a high degree of matching with a previously stored template image. In addition, a conventional object tracking method uses a relative difference method, in which template images are serially updated and the location of an object is identified based on a difference between a current frame and a previous flame. Furthermore, a conventional object tracking method uses a histogram matching method, in which the location of an object is identified based on a result of searching for an area having a high degree of matching with a color or luminance histogram of the object.
If the above-described pattern matching method is used, a still object can be searched at a high accuracy. However, the performance of tracking a moving object when the pattern matching method is used is not sufficiently high. More specifically, if the distance between an object and a tracking apparatus varies, if an object rotates, or if the orientation of the tracking apparatus itself varies, the pattern matching method cannot track the object at a high accuracy.
If the above-described relative difference method is used, if another object comes in front of a tracking target object or if the tracking target object has gone out of the scope of imaging, then the tracking target object may not be appropriately tracked.
If the histogram matching method is used, a moving tracking target object can be tracked but the performance of identifying the tracking target object is low if the identification is executed based on a color or luminance histogram only. Furthermore, the tracking performance of the histogram matching method is not sufficiently high if similar colors or areas having the approximately the same level of luminance is largely distributed in the background of an object.
In order to solve the above-described situation, Japanese Patent Application Laid-Open No. 09-181953 discusses a method for determining a characteristic color, which is uniquely used to a tracking target area and which can be securely extracted, considering the state of both a tracking target object and another object that is not a tracking target.
However, in the conventional method discussed in Japanese Patent Application Laid-Open No. 09-181953, a method for determining one characteristic color useful in using during tracking is discussed but the tracking may not always be executed at a high accuracy. More specifically, unless the state of the current tracking target object is useful in using during tracking, the probability of a wrong search may not be lowered if one optimum characteristic color is selected and used.